Operant Analysis of Striatal Lesions Deficits in Cognitive Tasks

It was Rosvold's experimental work in the 1950s that seriously challenged the concept of the striatum as a structure involved purely in motor function. Based on the topographical nature of projections from prefrontal cortex to the caudate nucelus, it was shown that caudate lesions in monkeys produced impairments on the same tasks that were known to be sensitive to frontal lesions.70 In particular, bilateral lesions of the caudate nucelus were seen to impair accuracy on Jacobsen's classic tasks of frontal function designed to assess spatial working memory, such as spatial alternation and delayed response.71-73

A corresponding functional organisation was demonstrated in the rat only when the prefrontal cortex came to be defined in terms of the projection areas of the mediodorsal nucleus of the thalamus — namely, to the medial and orbital walls of the frontal cortex rather than pole of the frontal lobe, as had previously been assumed.7475 Lesions in the rostral medial striatal areas that were innervated by medial wall prefrontal cortex again produced deficits in delayed alternation and spatial navigation tasks.76-78 It is these advances in functional neuroanatomy, as well as the neuropsychological deficits reported in basal ganglia disorders such as HD and PD, that provide the theoretical foundation for operant tasks designed specifically to assess the impact of striatal lesions on cognitive function.

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